My cams are also schrick, but one is for the m52tu and one for the m54 to get a more suitable overlap. Thats what I ment with interchangability. similar fit with different spec, sometimes even using the older parts as hop up part (like that s50 crank with stronger bearings, a modification some machinists also do, grinding the crank)
But when its updated as you say, doesnt that sound eerily similar to TU (technical Update)
In my book an m54 is an m52TUTU
Both the s54 as the m54 are both the end if their lineage and imho changes got smaller and smaller in each generation step.